September could be a good time to visit Key West, as the weather is generally fine. The average high temperature is around +30°C, and there are typically 2 sunny days in September. However, expect about 21 rainy days, and total monthly rainfall of approximately 173 mm. The weather is changeable so pack for every eventuality. Search flightsin one click on Avionero.
Good to know:
September is usually the hottest month of the year in Key West;
Average weather
☀️
+30°C
Avg. max. temperature
+23°C
Min.
+38°C
Max.
173 mm
Total precipitation
76%
Avg. humidity
3 m/s
Avg. wind
2 ☀️
Sunny Days
2 ⛅️
Cloudy
21 🌦
Rainy
Our opinion: Key West has OK weather in September.
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Average temperature in Key West in September
Here are the expected maximum, average and minimum temperatures in Key West for September based on the historical data.
Last Year
Historical Data
The expected average maximum temperature in September is +32°C with a maximum of +34°C and a minimum of +23°C.
The average maximum temperature goes down 9% by the end of the month, compared with the beginning of the month, from +32°C to +31°C.
Is Key West warm or cold in September?
Key West is typically warm in September.
Maximum temperatures go up compared to the previous month from +30°C to +30°C. The minimum temperature also goes up from +27°C to +27°C.
It’s generally warm, but pack a long-sleeve shirt for evenings.
September is the hottest month in Key West, here is the comparison with other months:
Climate in Key West in September
Key West weather looks like this, on average, in September and the surrounding months.
August
September
October
Avg. temperature
+30°C
+30°C
+28°C
Min. temperature
+23°C
+23°C
+16°C
Max. temperature
+35°C
+38°C
+33°C
Rainfall
129 mm
173 mm
133 mm
Wind
3 m/s
3 m/s
4 m/s
Humidity
75%
76%
76%
Air pressure
1015 HPa
1013 HPa
1013 HPa
Sunny days
3
2
6
Cloudy days
3
2
4
Rainy days
18
21
20
Snowy days
0
0
0
September weather is still as ok as in August.The temperature levels stay the same in the area of +30°C for average maximum temperature during the day.Prepare for more rain. Average rainfall goes from 129 mm to 173 mm.Humidity rises from 75% to 76%.The average wind speed doesn’t change much during September, staying around 3 m/s.The days becoming less sunny, going from 3 sunny days in August to 2 in September.
October brings much the same weather, it remains ok.
Wind speed in Key West in September based on historical data.
Last Year
Historical Data
The average wind speed is 3 m/s getting up to 6 m/s which is a medium breeze. You can feel it, especially getting out of the water.
The average wind speed in Key West is gradually increasing during September, going from 2 m/s to 4 m/s over the course of the month.
Rain
Amount of rainfall in mm during September in Key West based on historical data.
Last Year
Historical Data
Total precipitation in September is about 279 mm, with a 63% chance of rain on a typical day. The maximum amount of rainfall per day is around 38 mm, which is moderate rain.September is a pretty wet month with over 19 rainy days, so don’t forget to pack an umbrella, raincoat, and a pair of galoshes.
September is one of the rainiest months in Key West, here is a comparison with other months, total mm:
Key West wettest month is September, where a typical day has a 70% chance of precipitation and 173 mm of rainfall per day. February, on the other hand, is the driest month with a mere 32% chance of precipitation and 38 mm of rainfall per day.
How was the weather last September in Key West?
This is the weather in Key West in September 2025:
1 September
☀️
+32°C
2 September
☀️
+33°C
3 September
☀️
+32°C
4 September
☁️
+31°C
5 September
🌧️
+31°C
6 September
☀️
+32°C
7 September
☀️
+33°C
8 September
☀️
+32°C
9 September
☀️
+32°C
10 September
☀️
+32°C
11 September
☀️
+32°C
12 September
☀️
+34°C
13 September
☀️
+34°C
14 September
☀️
+34°C
15 September
☀️
+34°C
16 September
☀️
+33°C
17 September
☀️
+32°C
18 September
☀️
+34°C
19 September
☀️
+32°C
20 September
☀️
+32°C
21 September
🌧️
+30°C
22 September
🌧️
+32°C
23 September
🌧️
+30°C
24 September
🌧️
+31°C
25 September
🌧️
+32°C
26 September
🌧️
+31°C
27 September
🌧️
+31°C
28 September
🌧️
+30°C
29 September
🌧️
+31°C
30 September
☀️
+31°C
In September 2025 Key West had 19 sunny days, 1 cloudy days, and 10 rainy days. The average maximum temperature was +32°C, with an absolute maximum of +34°C and a minimum of +30°C. The average humidity was 73%, with a maximum of 97% and a minimum of 52%. The average wind speed was 3 m/s, with a maximum of 10 m/s and a minimum of 0 m/s.
Are you planning a trip in September?
Climate Change over Years
This is how Key West climate have been changing during last 43 years period.
The climate in Key West in September has not changed much over the last 43 years.
The average temperature was the lowest in 1981 (+25°C) and the highest in 2019 (+29°C). The driest year was 2009 with only 624 mm of rainfall, and the wettest year was 2024 with 1925 mm.
FAQ
Frequently asked questions about the weather in Key West in September:
Is September a good time to visit Key West?
It’s always a good time to visit Key West, but the weather is changeable in September, so plan a mix of indoor and outdoor activities and exploring, and pack for every eventuality.
Can you sunbathe in Key West in September?
September is warm in Key West. You may enjoy some beach or pool time in the day, but pack something a tad warmer for the evening.
Is Key West rainy in September?
Key West is often rainy in September. You may get a bit damp when outside, so pack an umbrella, and maybe even a raincoat.
Is it sunny in Key West in September?
Usually, it’s not very sunny in Key West in September, often it’s pretty cloudy. Pack for any eventuality; layering can help reduce the number of bulky items needed.
For this page, we’ve looked at the typical weather in Key West, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.
